1. Field of the Invention
The present invention relates to an electrode for an electrosurgical unit, and more particularly to, an electrode for an electrosurgical unit for the use in ablating and necrosing a living tissue by RF electric energy.
2. Description of the Related Art
A technique for piercing and inserting a long hollow tube-shaped electrode into a target living tissue and ablating (or coagulating) the living tissue by RF energy has been publicly known. In this case, when a current flows into the living tissue, the living tissue is heated, so that the living tissue and blood vessels are ablated by a more or less complicated biochemical mechanism. Such a process depends on ablation of a cell caused by thermal deformation of proteins in the cell over about 60° C. Here, the cell includes the tissue, blood vessel and blood. However, this technique has a problem in that the living tissue and blood around the electrode are excessively ablated and carbonized, and the carbonized living tissue around the electrode operates as an insulator which prevents extension of an ablation region of the living tissue.
In order to solve the foregoing problem, U.S. Pat. No. 6,210,411 discloses a technique for supplying saline solution through the inside of a hollow tube of an electrode, and discharging the saline solution to the outside via a porous body formed around a tip portion of the electrode. Like the above patent, techniques for discharging saline solution to the outside of an electrode prevent carbonization of a living tissue adjacent to the electrode by vaporization latent heat of the saline solution, and makes the saline solution soak into capillary vessels of the tissue around the electrode, to thereby improve electric conductivity and extend an ablation region of the living tissue. However, when a flow rate of the saline solution which can be infused into the living tissue increases, it has a detrimental effect on a patient. Therefore, since the flow rate of the saline solution which can be infused into the living tissue is restricted, if RF energy applied to the living tissue exceeds a limit point, carbonization of the tissue occurs around the electrode. As a result, this method also has a limit in extending an ablation region.
In addition, U.S. Pat. No. 6,506,189 discloses a technique for installing a saline solution tube in a hollow tube-shaped electrode with a closed tip portion, the saline solution tube having a smaller diameter than that of the electrode, and cooling the electrode by saline solution circulation that introduces saline solution into the inside of the electrode through the inside of the saline solution tube, makes the saline solution exchange heat in the electrode, and collects the saline solution through a space between the saline solution tube and the electrode. When RF energy is applied via the electrode, the nearest tissue to the electrode is mostly heated and possibly carbonized. As the electrode is water-cooled, the nearest tissue which is in contact with the electrode can be cooled and prevented from carbonization. Accordingly, it is possible to extend an ablation region of the living tissue. However, if RF energy applied to the living tissue exceeds a limit point, carbonization of the tissue occurs around the electrode. Consequently, this method also has a limit in extending the ablation region.
The aforementioned methods have been known as forming a spherical ablation region having a radius of about 2 cm from an electrode.
Meanwhile, Korean Laid-Open Patent No. 10-2004-0092614 filed by the present applicant suggests an electrode construction including a hollow electrode formed in a hollow tube shape with a mechanically-bored hole, a saline solution tube for introducing pressurized saline solution into the inside of the hollow electrode, and a flow control means for controlling a flow rate of saline solution discharged via the hole of the hollow electrode. According to the above patent, the pressurized saline solution flows from the outside of a living tissue to the inside of the hollow electrode through the saline solution tube, and cools the hollow electrode. The heat-exchanged saline solution is discharged to the outside of the living tissue, and some of the pressurized saline solution is discharged via the hole bored in the hollow electrode. A sheath tube having a hole bored alternately with the hole of the hollow electrode is covered on the hollow electrode, which prevents the pressurized saline solution from being emitted explosively to the outside of the living tissue. However, since it is difficult to couple the separate flow control means to the hollow electrode, there is an economical disadvantage. In addition, when the electrode inserted into the body is taken out, the flow control means may be separated therefrom. Moreover, the sheath tube may reduce a cooling effect of the pressurized saline solution. Further, since a diameter of the overall electrode, i.e. a thickness of a needle increases, when the electrode is inserted into the body, it causes severe bleeding.